The use of wooden poles in various utility systems throughout the world is extremely widespread. Such poles are usually treated with a fumigant and/or preservative before they are placed in the ground, but in most environments, the presence of moisture and pests slowly results in deterioration and decay of the pole proximate and below the groundline. Accordingly, currently there are literally millions and millions of wooden utility poles that are in various stages of decay and deterioration which will require their repair, reinforcement or replacement at significant expense.
While the problem of utility pole decay is greatest in connection with wooden poles, even metal poles and plastic coated metal poles can experience corrosion. In the broadest aspect, therefore, the method and apparatus of the present invention are useful in the reinforcement and/or repair of a section of pole, whether that pole is wooden, metallic or a composite pole.
The decay and rotting which occurs in wooden poles is usually confined to a depth of about two to three feet below the groundline. In most soils, rotting of a wooden pole below three feet will not occur because the conditions around the pole become anaerobic, i.e., they lack sufficient oxygen to support active rotting and decay. A utility pole will typically be buried to a depth of at least 10 percent of its length. A pole having a height in the range of about 25 feet to about 100 feet, for example, will be buried to a depth of about 51/2 feet to about 12 feet. It is possible, therefore, to repair a defective pole insitu if the pole can be reinforced from a position below the decayed section to a position above the decayed section.
While not entirely analogous, there are similar replacement problems faced in connection with underwater wooden pilings. The problems encountered in connection with repair of pilings insitu in a water environment (particularly in tidal installations) can be somewhat easier and are considerably different than the insitu repair of utility poles buried in the ground.
Considerable effort has been directed toward the repair of wooden and concrete pilings in a water environment. Typical of the repair apparatus and methods are the systems disclosed in U.S. Pat. Nos. 1,947,413; 2,385,869; 2,412,185; 3,708,146; 3,939,665; and 4,244,156. Common to these patented systems is the use of a sleeve assembly which is mounted to the pole or piling from a side thereof and extends along the length to be reinforced. Most usually the sleeve assembly is circumferentially spaced from the pole and acts as a mold into which concrete is poured. In some of these systems the shell or sleeve is removed, while in others it remains on the pole. While the concrete reinforces the pole, the sleeve assembly does not contribute to the reinforcement, since it is not bonded to the concrete. In U.S. Pat. No. 4,244,156, a foamed adhesive, such as polyurethane, is used to secure a protective plastic shell to a piling or pole, but the assembly is used to resist abrasion, not to reinforce the strength of the piling.
U.S. Pat. No. 968,798 discloses a similar shell-based pole repair system for the insitu repair of wooden, utility poles while buried in the ground. This patent discloses the use of a segmented shell that is positioned around the pole with a portion of the shell extending above the ground and a portion extending into a cavity around the pole below the ground. Reinforcing material is placed inside the shell, and a "plastic" material is poured into the shell and allowed to cure. Once cured, the shell is removed to leave the reinforced material around the pole. The plastic material in U.S. Pat. No. 968,798 is not specified, but undoubtedly is a material such as concrete, which does not need to be contained to be effectively molded and cured and which will easily release from the molding shell. The system does not employ the strength of the shell in effecting reinforcement of the pole.
Other more peripheral pole protection and/or repair systems are disclosed in U.S. Pat. Nos. 3,564,859 and 3,703,812.
A further prior art approach which has been employed is to mount a tapered or frusto-conical steel collar or sleeve around the pole with the small end supported on the ground and to rotate the collar down into the ground around the pole. The lower edge or small diameter of the steel collar has a jaw or blade construction which enables the collar to be rotated or screwed down into the ground. This system, however, requires a relatively heavy and expensive collar driving equipment, and there are many utility poles which are located at sites which will not permit the use of such equipment. Such collars are screwed into the ground to a depth of about three to four feet, and the upwardly diverging tapered cone can then be filled with a cement aggregate or a foam. When a foam is employed, the upper end of the cone is closed by a cap structure. The combined steel sleeve and aggregate are left in the ground around of the pole.
A further alternative, of course, has been the complete replacement of the pole. While the pole itself is not expensive to replace, the labor in connection with removal of the utility lines from the old pole and mounting of the same to the new pole is substantial.
Wooden utility poles conventionally have been installed proximate roads and highways. Such installations pose a serious hazard to motorists in the event that they should lose control of their automobiles. As highways are modernized and improved, utility poles are typically moved farther from the highways, but there are many situations in which such repositioning of utility poles is not possible or economically very burdensome.
One approach which can be taken to enhance the safety of utility poles proximate roadways is to provide poles which include a weakened or shear plane. The provision of a shear plane will result in transverse shearing of the pole by a relatively low force when the pole is struck by an automobile. In new metal pole installations this has been accomplished by mounting the pole to a base structure by a plurality of shear bolts. The bolts provide sufficient axial strenth to support the pole under all conditions except a lateral impact, for example, by an automobile.
The provision of a shear plane in wooden utility poles, however, is not as easily accomplished, particularly if the pole already is installed. One approach has been to drill holes in the sides of the pole to provide a weakened plane. The result, however, often has been to weaken the overall pole strength too much, and it is very difficult to control or predict the force which will shear the pole when using this technique.
Prior art utility pole repair, reinforcement and shear plane safety enhancement systems, therefore, have been found to have several disadvantages. The method and apparatus of the present inention seek to overcome these disadvantages and to provide an improved insitu pole repair, reinforcement and safety enhancement system which is particularly well suited for use with ground-supported, wooden utility poles.
More particularly, it is an object of the present invention to provide a method and apparatus for insitu repair of wooden utility poles which is relatively inexpensive and simple to use and yet provides a high strength reinforcement around a section of pole below the groundline.
Another object of the present invention is to provide a method and apparatus for insitu reinforcement of poles which does not require special complex equipment and can be employed by relatively unskilled personnel.
A further object of the present invention is to provide a method for insitu reinforcement of wooden utility poles which is compatible with conventional wooden pole fumigating procedures.
Another object of the present invention is to provide a method for reinforcement of wooden utility poles which is suitable for use with poles in virtually all terrains and environments.
Another object of the present invention is to provide a method and apparatus which enables the provision of a shear plane in a wooden utility pole.
A further object of the present invention is to provide a method and apparatus which is well suited to enhance wooden utility pole safety by the insitu reinforcement and provision of a shear plane in the pole.
A further object of the present invention is to provide a sleeve assembly which can be used by relatively unskilled personnel to rapidly and inexpensively form a reinforcement across a section of pole beneath the groundline while the pole remains supported by the ground.
Still another object of the present invention is to provide a method and apparatus for insitu reinforcement, repair and safety enhancement of a wooden utility pole which is a high-strength, durable and low-cost system.
The utility pole reinforcement and repair system of the present invention has other objects and features of advantage which will become apparent from and are set forth in more detail in the following description of the Best Mode Of Carrying Out The Invention and the accompanying drawings.